What Causes an Air Conditioner to Ice Up? Your Questions, Answered

One of the more peculiar things you might see during the summer is a buildup of frost or ice on your air conditioner. Considering the temperatures outside during the summer months, no one would blame you for your asking:

“Why is my air conditioner frozen?”

While the frost on air condition problem might seem unique, it’s actually very common. If you’ve ever wondered why it happens, keep reading for what causes an air conditioner to ice up.

How AC Works

Without diving into all the technical details, understanding why you may find your air conditioner frozen starts with understanding a little about how AC works.

The refrigerant is the core of the process. The refrigerant starts as a gas that gets compressed into a high-temperature liquid. This liquid passes into a condenser that helps remove heat.

The liquid goes into an evaporator where it returns to a cold gas state. This cold gas is what the AC unit uses to cool your home.

Poor Air Flow

An AC unit needs a stable airflow for it to work properly. Anything from debris around the unit to a dirty air filter can limit the airflow.

Blocked airflow means that the unit can’t access enough warm air for the evaporator coils to avoid freezing. The evaporator gets too cold and ices over. The good news is that clearing the blockage and letting the unit thaw should fix the issue.

Non-Stop Use

When the temperature climbs up to 90 degrees or more, you may turn the AC unit temperature way down and leave it on. Much like poor airflow, this non-stop use can also overtax the evaporator and cause a freeze over.

Dirty Evaporator Coils

Since most AC units sit outside or at least have partial outside exposure, the evaporator coils can get a buildup of dirt and grime. This buildup can be a little like putting insulation around the coils.

The warm air can keep reach them as well, which lets the coils ice over. You can attempt a coil cleaning yourself, but an HVAC pro can likely do it faster and better.

Low Refrigerant

When an AC unit runs low on refrigerant, the system can’t maintain the proper pressure. Instead of converting back to a cool gas at the evaporator, it happens early. The system isn’t designed for that and ices over.

Always enlist an HVAC pro to add refrigerant to your AC unit.

Parting Thoughts on What Causes an Air Conditioner to Ice Up

What causes an air conditioner to ice up is a good question because frost means something has gone wrong. Even worse, you can end up damaging the AC unit if the system keeps running when iced over.

The problem might stem from a low refrigerant level, dirty coils, poor airflow, or non-stop use. It might even happen due to a mechanical failure somewhere else in the unit.

You should generally leave fixing an iced-over AC unit to an HVAC pro because so many things can cause the problem.

Design Air specializes in AC maintenance and repair for Riverside County, California. If you’re dealing with an iced-over AC unit, contact us today for an appointment.